#define _CRT_SECURE_NO_WARNINGS 1
//拷贝函数（传统写法）
//string s2(s1) 或  string s2 = s1
string(const string& s)
{
	_str = new char[s._capacity + 1];
	strcpy(_str, s._str);
	_size = s._size;
	_capacity = s._capacity;
}